Age Group Comparisons in Category Member Generation Tasks: Effect of Stimulus Design Keith M' McGreg

1
Age Group Comparisons in Category Member
Generation Tasks Effect of Stimulus DesignKeith
M. McGregor1,3, Michelle L. Benjamin1,2, Yu-Ling
Chang1,2, Zvinka Zlatar1,2, Colin Rackelman1,2,4,
Megan Gaiefsky1,2, Ilana Levy 1,2, Keith D.
White1,3,4, and Bruce Crosson 1,2,4Department of
Veterans Affairs Rehabilitation Research and
Development Brain Rehabilitation Research Center
at the Malcom Randall VA Medical
Center1University of Florida Departments of
Clinical and Health Psychology2, and
Psychology3,and McKnight Brain Institute4,
Gainesville, FloridaPresented at the February
2008 International Neuropsychological Society
Conference, Waikoloa, HawaiiThis poster is
available on the Web at http//www.BIRC.phhp.ufl.e
du
INTRODUCTION
RESULTS
Age Group Comparison

• Optimal stimulus presentation paradigms in
  functional magnetic resonance imaging (fMRI)
  continues to be vital to experimental design
  particularly in the study of language processes.
• Category member generation tasks have indicated a
  relationship between activation between lateral
  inferior and medial frontal areas and the basal
  ganglia (Crosson et al., 2003 Crosson et al.,
  2005), a finding with particular relevance to the
  imaging studies of aging and stroke
  rehabilitation.
• The imaging of such word generation tasks for
  between group comparisons has been reported using
  both block (Crosson et al., 2003) and
  event-related paradigms (Crosson et al., 2005
  Wierenga 2007), but we are not aware of research
  comparing the sensitivity of different paradigm
  designs on group activation comparisons,
  particularly in inferior frontal and subcortical
  areas.
• The present study compares age related
  differences in activation across event related
  and block design fMRI during word retrieval
  (category member generation) tasks.

Word Generation Comparison to Baseline
Event-related
Block
R
L
R
L
R
L
Talairach montage of task-to-baseline activation
comparisons conjunction analysis of Age at Block
(top) and Event-related (bottom) comparisons _at_
plt.0001 Blue indicates Older activation Yellow
indicates Younger activation Green indicates
Both Older and Younger activation
Block
METHODS
Subjects Twenty-two neurologically normal older
adults at least 65 years of age and 22 young
adults between 18-35 years of age were recruited
from the community and participated in two fMRI
category exemplar tasks (BLOCK EVENT). Older
subjects were given a short mental status
screening (MMSE) to screen for possible dementia
and Mild Cognitive Impairment all older subjects
scored gt 27 on the MMSE. See Table 1 for
descriptive demographics. Table 1. Group
Demographics
R
L
Event-related
Talairach montage showing group activation
comparisons _at_ plt.005 Blue indicates Older gt
Younger Orange indicates Younger gt Older

• fMRI Experimental Procedures
• Baseline visual fixation task with simultaneous
  audio and visual presentation of category
  exemplars and stop cue during active trials in
  both fMRI paradigms.
• 60 total categories presented only once across
  BLOCK and EVENT conditions.
• EVENT Condition
• Overt, single-item response, event-related fMRI
  of category-member generation for 44 categories
  across 4 fMRI runs (e.g., eagle for birds).
• 3.4 seconds/category for each active exemplar
  generation event.
• Resting blocks of 15.3, 17, 18.7, and 20.4 secs
  between active trials.
• BLOCK Condition
• Covert, multiple-response, block paradigm fMRI of
  category-member generation for 16 total
  categories across 2 fMRI runs.
• 17 seconds/category for each active exemplar
  generation block.
• Resting blocks of 10.2, 11.9, and 15.3 seconds
  between active blocks.
• fMRI Acquisition 3 T Siemens Allegra instrument,
  gradient echo planar images.
• Functional images 240mm FOV, 64x64 matrix, 3.8mm
  x 3.8mm in-plane resolution, TR1700 ms, TE25
  ms, flip angle70. Whole-brain slice coverage
  using 32 5mm thick slices (BLOCKaxial
  acquisition EVENTsagittal acqusition).
• High-resolution T1-weighted 3D MP-RAGE axial scan
  (TE 4.13 ms TR 2000 ms FOV 240 mm FA
  8 matrix size 256x192 128 1.3mm slices).
• fMRI Analyses AFNI
• FWHM spatial-smoothing at 4mm.
• 3dDeconvolve Deconvolution analysis with
  response estimate (maxlag) of
• EVENT 12 images omitting the first two responses
  (minlag)
• BLOCK 20 images

CONCLUSIONS
REFERENCES

• Acknowledging methodological differences in
  response production (i.e. overt versus covert),
  the data indicate that block paradigms with
  covert response may provide greater sensitivity
  to lateral frontal and basal ganglia activation
  in healthy adults during category member
  generation tasks.
• However, event-related FMRI paradigms will
  continue to have relevance in studying certain
  patient populations in which on-line task
  performance needs to be carefully monitored
  (e.g., language production in nonfluent aphasia
  Crosson et al, 2007).
• On-line task performance may be beneficial for
  neurologically normal populations, since
  different subsets of healthy individuals may show
  different patterns of neural activation to
  complete a task. E.g., Wierenga et al (2007)
  high-functioning old subjects showed a positive
  correlation between naming accuracy and right
  inferior frontal cortex (IFC), whereas
  low-functioning old subjects and young subjects
  showed a negative correction in right IFC all
  groups showed positive correlations between
  accuracy and left IFC activity.
• Additionally, overt response monitoring within an
  event-related imaging paradigm may provide
  fruitful secondary analysis strategies for a
  better understanding of language functions
  complex interactions and delineated task-related
  contributions of specific brain areas (e.g.,
  correct vs. error response comparisons).
  (Meinzer et al., 2006)

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J. R., Moore, A. B., Wierenga, C. E., Gopinath,
K., Soltysik, D., Bauer, R. M., Auerbach, E. J.,
Gokcay, D., Leonard, C. M., Briggs, R. W.
(2003). Left and right basal ganglia and frontal
activity during language generation
Contributions to lexical, semantic, and
phonological processes. Journal of the
International Neuropsychological Society, 9,
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Acknowledgements of support VA RRD Center of
Excellence Grant F2182C and Research Career
Scientist Award (Crosson) McKnight Brain
Institute of University of Florida E. F. McKnight
Grants.